How much variation are you seeing at opamp input and amux input pins ? Are you getting the outputs near the expected range ? Could you please let me know the output observed at your end ?,
If I fix my input to the OpAmp at 100mV and select channel 3 of the AMux (gain = 2), I receive 20mV at the output of the OpAmp.
If I remove the Amux and hardwire in a 1K ohm resistor, I receive the correct value of 200mV. So I suspect the AMux.
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This is caused by the routing resistance inside the chip.
For example, the resistance between the Pin_1K pin (P2) and the Pin_14K pin (P3) is estimated as 2150homs.
This resistance value cannot be ignored as the feedback resistor network.
It is recommended not to flow much current through the AMXU.
Please adjust the resistance value of the output voltage divider.
Thanks for your reply. I don’t thing the issues I’m having are a result of internal resistance. The circuit is acting like an attenuator. I input 100mV and receive 20mV at the output with the 1K feedback resistor switched in.
Also, I’m not running a lot of current through the AMux. I feel like the Amux circuits are not performing as they should. Is the 4100PS a new device? Should I try other devices?